Rhombodinium ?minus He Chengquan, 1991, p.99, pl.36, fig.5. Holotype: He Chengquan, 1991, pl.36, fig.5. Questionable assignment: Williams et al. (2015, p.311). Age: middle Eocene.

Description from He Chengquan, 1991, translated by Suning Hou, 07-01-2019
Description: The cyst is dorsal-ventral flattened, contour pentagon, lateral elongated, the edge is nearly straight, longer than the width. The apical horn is blunt, length 5-7.5μm, two antapical horns are small, conical, nearly equal, 10μm long, blunt end, close to each other (18-22.5μm); 2 lateral horns are obvious, length 10-12.5μm, tapering distally, the end is concave, cingulum fuzzy, only slightly displayed in the lateral horns. Outer wall surface granular, fine or coarse, sometimes ornamentation on the horns is obvious. Inner body contour is oval - round rhombus, more or less convex into the lateral horns, wall surface smooth; It has been separated from the outer wall. The archeople is intercalary, the outline is round trapezoid, length larger than width. The operculum has been separated and preserved in situ. Cyst length 80-85μm, width 82-105μm, the inner body length 65-70μm, width 65-77μm (measured 3); Holotype length 82.5μm, width 88μm , Inner body length 69μm, width 67.5μm.
Comparison: this species differs from Rhombodinium wuqiaense in small individuals, 2 antapical horns not diverging and close to each other; this species differs from R. kunlunense in its coarse granular outer wall surface;
Location and stratigraphy: Shache County Altashi; Wulagen fm.